Objective: To design methods for improving human hybridoma development; characterize human anti rabies virus mAbs capable of neutralizing virus, cloning of the Fab domains of these mAbs in heterologous systems; elucidate the mechanism(s) by which polyreactive antibodies recognize a variety of different antigens. Major Findings: We have successfully cloned several different human monoclonal antibody Fab domains in E. Coli. One of these recombinants, derived from a mAb cell line (mAb57) capable of neuralizing rabies virus in vitro and in vivo, maintained virus neutralizing activity in vitro. In vivo activity has yet to be tested. We have developed 10 new anti-rabies virus mAbs which recognize the surface glycoprotein "G" of rabies. These antibodies will be screened for virus neutralization activity. We have also cloned and characterized two human anti-HIV-1 Fab domains derived from mAbs. One Fab (M7B5) binds to the HIV-1 gp120 protein and the second Fab (T15G1) binds to HIV-1 gp41. In efforts aimed at defining the mechanism by which polyreactive antibodies recognize multiple antigens we have determined that the constant domain DNA and amino acidsequences of polyreactive antibodies do not differ from monoreactive antibodies and that the degree of glycosylation in these antibodies does not change their antigen recognition profile.